Dually responsive multinetworked hydrogels with improved performances by covalently bonding poly(N -isopropylacrylamide)-based microgels and poly(vinyl alcohol) skeleton

To prepare intelligent hydrogels with both good mechanical performance and fast response, a series of multinetworked composite hydrogels with pH and thermo-responsivity were designed and fabricated combining the advantages of both interpenetrating polymer network hydrogels and microgels. To begin with, precipitation polymerization of N-isopropylacrylamide, methacrylic acid and polyethyleneglycol methacrylate was carried out in poly(vinyl alcohol) (PVA) aqueous solution, yielding thermo- and pH-responsive copolymeric microgels. Then glutaraldehyde was added to the obtained microgel dispersion to covalently bond the microgel particles and PVA through acetal reaction, leading to the formation of multinetworked hydrogels with dual responses. The morphology of microgels and the internal microstructure of composite hydrogels were characterized by transmission electron microscope and scanning electron microscope, respectively. The influence of the PVA content and glutaraldehyde dosage on the mechanical behavior of the prepared hydrogels was investigated by means of uniaxial compressive tests. Experimental results reveal that the as-prepared composite hydrogels exhibit enhanced mechanical performance compared to conventional hydrogels. Investigation onthe swelling and deswelling behaviors shows that they possess good temperature- and pH-sensitivity andswell/deswell more rapidly than conventional hydrogels. POLYM. COMPOS., 2012. © 2013 Society of Plastics Engineers